Alternating-current motor.



PATENTED MAY 15, 1906.

A. W. SOHRAMM.

ALTERNATING CURRENT MOTOR.

APPLICATION FILED MAY 20, 1905.

2 SHEETS-SHEET 1.

. No. 820,890. PATENTED MAY 15, 1906.

A. w. SGHRAMM.

ALTERNATING CURRENT MOTOR.

APPLIOATION FILED MAY 20, 1905.

2 SHEETS-SHEET 2.

unrrnn STATES PATENT oriuon.

ADOLPH W. SOHRAMM, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO ELEOTRO DENTAL MANUFACTURING COMPANY, PHILADEL- PHIA. PENNSYLVANIA, 'A CORPORATION OF PENNSYLVANIA.

AEET EPZNATlNG=GURRENT MOTOR.

Specification of Letters Patent.

' Patented. May 15, 1906.

Application filed ay 20, 1905. Serial No. 261,381.

To all whom, it may concern:

Be it known that I, AnoLPn W. SoHnAr i r, a citizen of the United States, residing in Philadelphia, Pennsylvania, have invented tion of its armature-shaft is retarded, as by.

the application of a load.

Another object of the invention is to provide a motor having the above-noted characteristics, with suitable means for varying its speed, the construction of the motor being such that it shall be reversible, have large starting torque, and practically no sparking at its brushes.

These objects I attain as hereinafter set forth, reference being had to the accompany ing drawings, in which- Figure 1 is a diagram illustrating one form of my impro ved motor and the connections therefor. Fig. 2 is a special form of the invention, illustrating an arrangement of parts whereby the number of available speeds at which it is possible to operate the motor may be increased. Figs. 3 and a are diagrams illustrating the use of non-inductive instead of inductive resistance in connection with my motor. Pig. 5 is a diagram illustrating the connections for operating my inotor as a reversing-machine, and Figs. 6 and '7 are respectively a plan and a vertical section illustrating the detail construction of a portion of the preferred form of controller for use with the motor shown in the other figures.

in carrying out my invention ll provide a commutator-rnotor with two windings, which I shall respectively term the main and the corrective fieldwindings, the number of turns in the latter of these being properly proportioned relatively to those of the main winding in order to obtain the desired speed torque characteristic and the function of this corrective winding being to set up a magnetomotive force which changes the magnitude and phase of the field lluX.

The drop in voltage in the corrective circult is the resultant of the impressed or line voltage, the electromotive force induced by the field flux and the electromotive force due to the reactance of the inductive resistance,

this latter being preferably equal to zero for the lowest speed of the motor. The speed. and power of the motor will be de endent upon the main field-Winding, and w 'le said speed may be varied between certain limits by varying the amount of inductive resistance in circuit still further variations may be obtained by varying the number of main field-turns in circuit.

Referring to Fig. l of the above drawings, A is the armature of the motor, of which B is the main field-Winding, and O the corrective field-winding. D is the speed-controller, preferably consisting of a lever d, which may e turned in any direction to engage any of the contact-buttons d and d Said contactlever is permanently connected to one of the current-supply mains and is of such dimensions that it simultaneously engages, and

thereby connects to, said supply-main oppo-- site pairs of the contacts (1 and (1 These contacts preferably have between them projecting buttons d as shown in Figs. 6 and 7,

which are usually of greater height than said.

contacts and so placed that as the lever d is turned it is first forced to break contact with one pair of the contacts d and d by being raised to pass over the adjacent pairs of but,- tons d it. is then free to move down into engagement with the next pair of contacts and may either be of resilient material or constructed in any other manner, so as to be free to move toward and from the surface upon which the contacts and insulating-buttons are mounted. This construction prevents short-circuiting any of the windings and is burther designed for the purpose of providing a definite stop for'each speed point and also for compelling a quick passage from one speed point to the next.

E represents a body of inductive resistance connected at dillerent points of its length to various ones of the contacts 01 of the controller D. The contacts (1 of said controller are connected together and to one terminal of the armature A, whose second terminal is, as shown, connected to one end of the main field-winding B. Both main and corrective windings are connected to the second supplymain.

While the motor is not in use, the contactlever rests upon a pair of dead contacts, as shown in Fig. 1, and when said lever is moved into en agement with a pair of the contacts d and 2 the motor will operate at a definite speed, which will be varied as said lever is moved into engagement with other pairs of said contacts.

As above noted, if a greater number of speed variations be desired, or if it be desired to vary the speed between wider limits, the s ecial arrangement of the motor shown in ig. 2 maybe employed. In this case, as in that illustrated in Fig. 1, the winding E is connected at various points of its length to the four contacts (1 of the controller D, and

each of these contacts is respectively connected to other contacts d arranged in an arc of the same circle as that defined by the contacts d Upon arcs of a concentric circle are placed two segmental contact-pieces d and d of which one is connected to one end or the main. field-winding B, while the second is connected to some point in the length of the same winding, depending upon the characteristics of the particular motor to be operated and the speed variation desired. The opposite end of the main field-winding is connected to the armature A, which with one end of the corrective field-winding C is connected to a supply-main; As before, the second supply-main is connected to a contact-lever d, which is of such dimensions as to simultaneously engage any one of the contacts d or d and the adjacent contact-segments or d, as the case may be.

Under operating conditions it will be seen that the speed of the motor can be varied within the limits possible in the case illustrated in Fig. 1 by moving the lever d into engagement with the various contacts (1 and contact-segment d. In addition the motor may be made to operate through a second series of speed variations by moving said handle into engagement with the contact d" and the contact-segment (1 As shown in Fig. 3, I may employ non-inductive resistance E in place of the inductive resistance E, if this should for any reason be found desirable, the same change being made in that arrangement of my system shown in Fig. 4i, in which the number of turns of the main winding is altered simultaneously "with the change of resistance in series with the corrective winding. This end is secured by providing two segmental contacts d and d", arranged concentrically with the contacts (Z and so placing them in relation to' the con tact-lever (Z that it is possible for said lever to engage but two of said contacts a while itis in engagement with the segment (1 the remaining two segments (1 being engaged by the lever, and hence connected to the supplymain as long as it is in engagement with the segment (1 Since the brushes are ordinarily placed at the neutral point, the motor may be operated as a reversing-machine, and with this arrangement the same flux distribution is secured for both directions of rotation. Any desired form of reversing-switch may be employed, such as is shown diagrammatically at F in Fig. 5.

I claim as my invention 1. An alternating-current motor having main and corrective field-windings, and means for varying the speed of the motor, said means including a device for varying, through a number of steps, the current-flow in the corrective field-circuit, and for varying the number of turns of the main field-winch ing in circuit, substantially as described.

2. An alternating-current motor having main and corrective field-windings and means for varying the s eed of the motor, said means including a evice for varying, through a number of steps, the current-flow in the corrective field-circuit for each of a plurality of arrangements of the main field-winding, substantially as described.

3. An alternating-current motor having a main field-windin'g in series with its armature, a corrective winding placed to vary the ma nitude and phase of the flux set up by sai main field-winding, current-modifying means in series with the corrective winding, and a controlling device having connections for varying the number of turns of the main field-winding and the amount of the currentmodifying means in circuit, substantially as described.

i. A11 alternating-current motor having a main field-winding in series with its armature, a corrective winding connected in parallel to the armature and main iield-winding, and placed to vary the magnitude and phase of the flux set up by said main field-winding, an inductive winding in series with the corrective winding, and a controlling device having connections for varying the number of turns of the main field-winding and of the inductive winding in circuit, substantially as described. I

5. An alternating-current motor having a main and a corrective field-winding, currentmodifying means, and a controller connected to var the amount of the main field-winding and a so the amount of the current-modifying means in circuit, substantially as described.

6. An alternating-current motor having main and corrective field-windings, currentmodifying means in circuit with the corrective winding, and a controller for governing the amount of said means in circuit, said controller including a rotatably-supported arm connected to a current-supply main, a series of contacts connected to different points on the current-modifying means, and a second series of contacts connected to the main fieldwinding of the motor, substantially as described.

7. An alternating-current motor having main and corrective field-windings, currentmodifyingmeans in circuit With the corrective winding, and a controller for governing the amount of said means in circuit, said controller including an arm and contacts whereby both the main and corrective field-circuits -may be simultaneously connected to a current-supply main or simultaneously broken, substantia ly as described. 8. An alternating-current motor having a 'main and a corrective field-winding, currenttroller, current-modifying windings connected at various points of their length to one set of contacts, and the main field-winding having a plurality of connections respectively to the other set of contacts, substantially as described.

10. An alternating-current motor having a main and a corrective field-Winding, an inductive resistance in circuit with said corrective field, and a controller for varying the amount of said resistance in circuit, said controller having a number of contacts, and having pieces placed to cause one contact or set of contacts to be disen aged before the circuit can be completed t ou h another con-, tact or contacts to prevent s ort circuiting of successive contacts, substantially as described.

11. An alternating-current motor having a main and a corrective field-winding, currentmodifying means in circuit with the corrective Winding, and a device for varying the amount of said means in circuit, said device including pieces for simultaneously breaking the circuits of the main and corrective windings between successive positions, substan tially as described.

. In testimony whereof I have signed my name to this specification in the presence of two subscribin witnesses. I

DOLPH W. SOHRAMM. Witnesses: v

WILLIAM E. BRADLEY, Jos. H. KLEIN. 

